At present, a transition is taking place, at least in the development, from the conventional synchronous time-division-multiplex, which is now called Synchronous Transfer Mode STM, to a new transmission mode, the Asynchronous Transfer Mode ATM. With both STM and ATM, the messages to be transmitted are divided into small information units, compressed temporarily and transmitted together with similar information units from other messages.
With STM, the affiliation .of the individual information units with a certain message is established by the periodically returning (synchronous) position inside the data stream. The exchange takes place, among others, by a predetermined time shift in the position of the information units.
In the ATM, the affiliation of an information unit with a certain message cannot be determined from the position in the data stream, and must therefore be specially identified. For that reason, each of the information units is compiled into a data packet by a header. In the ATM, these data packets are called cells.
During the certainly long transition time, STM and ATM will appear together and transition installations between STM and ATM will be created. Packetizers and depacketizers are a known solution for this problem. The packetizers and depacketizers described in principle in FIGS. 7 and 8 of DE 38 16 747.6 A1, are only cited here as an example.